Materials such as silicon oxide (SiOx), silicon carbide (SiC), and carbon doped silicon oxide (SiOCx) films find widespread use in the fabrication of semiconductor devices. One approach for forming such silicon-containing films on a semiconductor substrate is through the process of chemical vapor deposition (CVD) within a chamber. For example, a chemical reaction between a silicon supplying source and an oxygen supplying source may result in deposition of solid phase silicon oxide on top of a semiconductor substrate positioned within a CVD chamber. As another example, silicon carbide and carbon-doped silicon oxide films may be formed from a CVD reaction that includes an organosilane source including at least one Si—C bond.
Water is often a by-product of such a CVD reaction of oganosilicon compounds. As such, water can be physically absorbed into the films as moisture or incorporated into the deposited film as Si—OH chemical bond. Either of these forms of water incorporation is generally undesirable. Accordingly, undesirable chemical bonds and compounds such as water are preferably removed from a deposited carbon-containing film. Also, in some particular CVD processes, thermally unstable organic fragments of sacrificial materials (resulting from porogens used during CVD to increase porosity) need to be removed.
One common method used to address such issues is a conventional thermal anneal. The energy from such an anneal replaces unstable, undesirable chemical bonds with more stable bonds characteristic of an ordered film thereby increasing the density of the film. Conventional thermal anneal steps are generally of relatively long duration (e.g., often between 30 min to 2 hrs.) and thus consume significant processing time and slow down the overall fabrication process.
Another technique to address these issues utilizes radiation such as infrared (IR), ultraviolet (UV), or visible radiation to aid in the post treatment of CVD-produced films such as silicon oxide, silicon carbide, and carbon-doped silicon oxide films. For example, U.S. Pat. Nos. 6,566,278 and 6,614,181, both to Applied Materials, Inc. and incorporated by reference herein in their entirety, describe the use of UV light for post treatment of CVD carbon-doped silicon oxide films. The use of UV radiation for curing and densifying CVD films can reduce the overall thermal budget of an individual wafer and speed up the fabrication process. A number of various UV curing systems have been developed which can be used to effectively cure films deposited on substrates. One example of such is described in U.S. application Ser. No. 11/124,908, filed May 9, 2005, entitled “High Efficiency UV Curing System,” which is assigned to Applied Materials and incorporated herein by reference for all purposes.
During these curing techniques, as well as other such procedures, it is common for water molecules and various other species to be outgassed or otherwise released from the film or material being cured or processed. These species tend to collect on various exposed surfaces of the chamber, such as windows in the chamber, that can reduce the efficiency of the process. Further, the build-up of these species on the surfaces requires periodic cleaning of the chamber surfaces, such as after every 200 wafers processed, which results in significant tool downtime and a corresponding reduction in manufacturing throughput. The contamination levels after processing typically are used as a benchmark for cleaning intervals. It generally is desirable to have a high MWBC value (mean wafer between clean), or mean number of wafers processed between cleanings, in order to reduce costs and system downtime. In some swept source systems, for example, a MWBC of 800-1200 wafers is considered to be an undesirably low value of MWBC, caused by factors such as the condensation of outgassed materials on relatively cold surfaces of the processing chamber.
For reasons including these and other deficiencies, and despite the development of various curing chambers and techniques, further improvements in this important technology area are continuously being sought.